In land based aquaculture systems there is often a need to transfer marine animals from one tank or receptacle to another. This may be done for grading purposes or to allow cleaning of, and removal of waste products and debris from, a tank. For example in the harvesting of crustacean larvae, the larvae must be regularly shifted from tank to tank to allow cleaning. At present, this is performed by manually transferring the larvae by a pipette to a holding vessel. The larvae are particularly stress sensitive and it is common for a large proportion to die during this procedure. On the other hand, if the larvae are not transferred, to allow cleaning of the tank and removal of waste products, significant proportions will die due to water pollution. The greater the time between successive cleanings of the tank the greater the proportion of larvae that die. Liquid handling is also important in water treatment plants, refineries and mineral processing plants. In many instances, it is important not only that liquid be transferred but that it be transferred in a controlled manner with relatively low flow rates to prevent mixing or stirring of any particles or other matter held within the liquid.